Method for manufacturing foldable backplate film

ABSTRACT

The present application relates to a method for manufacturing a foldable backplate film, and according to one aspect of the present invention, a method for manufacturing a foldable backplate film that the foldable backplate film is manufactured by a method of cutting it in a direction from the release film to the protective film upon half-cutting, and then release-changing the release film to an extended release film, whereby by improving a half-cutting process, the release film is not peeled off due to the sticking-out of the pressure-sensitive adhesive upon product handling and transportation, or the foldable backplate does not fall off upon the release film peeling, is provided.

TECHNICAL FIELD

The present application relates to a method for manufacturing a foldablebackplate film.

The application is a 35 U.S.C. 371 National Phase Entry Application fromPCT/KR2022/002492 filed on Feb. 21, 2022, which claims the benefit ofpriority based on Korean Patent Application No. 10-2021-0025030 filed onFeb. 24, 2021 with the Korean Intellectual Property Office, all of thedisclosures of which are incorporated herein by reference in theirentirety.

BACKGROUND OF THE INVENTION

Recently, with the development of display-related technologies, displaydevices, which are deformable in the use stage, such as folding, rollingin a roll shape, or stretching like a rubber band, have been researchedand developed.

The deformable display device may not only be transformed into a presetshape, but may also be transformed into various shapes in accordancewith a user's request or in conformity with a situation in which thedisplay device is used. Therefore, it is necessary to recognize thedeformed shape of the display and control the display device in responseto the recognized shape.

Meanwhile, the deformable display device has a problem in that eachconstitution of the display device is damaged according to thedeformation, the respective constitutions of the display device mustsatisfy folding reliability and stability.

In particular, recently, flexible substrates are mainly used forthinning the display, where since the display panel using the flexiblesubstrate is too thin, a foldable backplate film capable of supportingthe display panel is attached to the lower part of the flexiblesubstrate and used.

FIG. 1 is a vertical cross-sectional view showing an existing foldablebackplate film; FIG. 2 is a plan view of the existing foldable backplatefilm; FIG. 3 is a diagram exemplarily illustrating a method formanufacturing method an existing foldable backplate film; and FIG. 4 isa diagram for explaining the pressure-sensitive adhesive sticking-outphenomenon of the existing foldable backplate film.

The existing foldable backplate film has a structure of a release film(1)/a pressure-sensitive adhesive layer (2)/a foldable backplate (3)/aprotective film (4), and in a process of manufacturing the foldablebackplate film, a cutting process of cutting the foldable backplate filminto a two-piece cell size along the cutting line (S2) is performed sothat it consists of the body part (S1) attached to the screen part ofthe panel and the pad part (S3) attached to the lower part for DIbonding.

Referring to FIG. 3 , the conventional cutting process was carried outby performing half-cutting in the direction from the foldable backplateto the release film and then attaching the protective film. As describedabove, in the conventional foldable backplate film manufactured byhalf-cutting, a groove (H1) is formed in the release film.

However, in the foldable backplate film manufactured through such acutting process, there was a problem that the release film did not peeloff due to the sticking-out of the pressure-sensitive adhesive (see A inFIG. 4 ) upon product handling and transportation, or the body part orthe pad part of the foldable backplate film came with upon the releasefilm peeling process.

BRIEF SUMMARY OF INVENTION

The present application relates to a method for manufacturing a foldablebackplate film, which can prevent a problem that a release film does notpeel off due to sticking-out of a pressure-sensitive adhesive uponproduct handling and transportation, or the backplate comes with uponthe release film peeling process, by improving a half-cutting process.

In one embodiment of the present application, a method for manufacturinga foldable backplate film comprising steps of: preparing a foldablebackplate comprising a base film and a pressure-sensitive adhesive layerprovided on one side of the base film; attaching a first release film tothe opposite side of the side of the pressure-sensitive adhesive layerin contact with the base film; attaching a protective film to theopposite side of the side of the base film in contact with thepressure-sensitive adhesive layer; half-cutting the foldable backplatein a direction from the first release film to the protective film alonga cutting line dividing a body part and a pad part; peeling the firstrelease film after the half-cutting step; and attaching a non-cut secondrelease film to the position where the first release film has beenpeeled off to manufacture a foldable backplate film is provided.

Advantageous Effects

In the method for manufacturing a foldable backplate film according toone example of the present application, the foldable backplate film ismanufactured by a method of cutting it in a direction from the releasefilm to the protective film upon half-cutting, and then release-changingthe release film to an extended release film, whereby it is possible toprevent the problem that the release film is not peeled off due to thesticking-out of the pressure-sensitive adhesive upon product handlingand transportation, or the backplate comes with upon the release filmpeeling.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a vertical cross-sectional view showing an existing foldablebackplate film.

FIG. 2 is a plan view of the existing foldable backplate film.

FIG. 3 is a diagram exemplarily illustrating a method for manufacturingan existing foldable backplate film.

FIG. 4 is a diagram for explaining the pressure-sensitive adhesivesticking-out phenomenon of the existing foldable backplate film.

FIG. 5 is a diagram exemplarily explaining the method for manufacturinga foldable backplate film according to the present invention.

FIG. 6 is a diagram showing a foldable backplate film manufactured bythe manufacturing method shown in FIG. 5 .

FIG. 7 is a plan view of the foldable backplate film shown in FIG. 6 .

DETAILED DESCRIPTION OF INVENTION

Hereinafter, this specification will be described in more detail.

In this specification, when any part “comprises” a certain component, itmeans that other components may be further included, rather thanexcluding other components, unless otherwise stated.

Examples of the present invention will be described in detail withreference to the accompanying drawings so that those having ordinaryknowledge in the technical field to which the present invention pertainsmay easily practice it. However, the present invention may be embodiedin several different forms, which is not limited to the examplesdescribed herein.

FIG. 5 is a diagram exemplarily explaining a method for manufacturing afoldable backplate film according to the present invention, FIG. 6 is adiagram showing a foldable backplate film manufactured by themanufacturing method shown in FIG. 5 , and FIG. 7 is a plan view of thefoldable backplate film shown in FIG. 6 .

The method for manufacturing a foldable backplate film according to oneexample of the present application comprises steps of: preparing afoldable backplate comprising a base film (100) and a pressure-sensitiveadhesive layer (200) provided on one side of the base film (100);attaching a first release film (300) to the opposite side of the side ofthe pressure-sensitive adhesive layer (200) in contact with the basefilm (100); attaching a protective film (400) to the opposite side ofthe side of the base film (100) in contact with the pressure-sensitiveadhesive layer (200); half-cutting the foldable backplate in a directionfrom the first release film (300) to the protective film (400) along acutting line dividing a body part and a pad part; peeling the firstrelease film (300) after the half-cutting step; and attaching a non-cutsecond release film (500) to the position where the first release film(300) has been peeled off to manufacture a foldable backplate film.

In addition, at least one width (L1) of the second release film (500) isgreater than a width (L2) of the foldable backplate.

The existing manufacturing method performs a process of half-cutting itin a direction from the backplate to the release film and then attachinga protective film thereto, whereas the manufacturing method according tothe present invention performs half-cutting it from the direction of therelease film to the direction of the protective film, followed bypeeling the cut first release film (300) and then release-changing itwith an extended and non-cut second release film (500) in the firstrelease film (300), whereby the sticking-out of the pressure-sensitiveadhesive is prevented upon product handling and transportation, and thusthe release film peeling is prevented, and moreover, it is possible toprevent a problem that the backplate comes with when the release film ispeeled for product application.

Due to the difference in these manufacturing methods, there is adifference that the foldable backplate film manufactured according tothe existing manufacturing method has a groove (H1) formed on therelease film (1) by half-cutting, whereas the foldable backplate filmmanufactured according to the manufacturing method of the presentinvention has a groove (H2) formed on the protective film (400) byhalf-cutting.

A difference (L1-L2) between at least one width of the second releasefilm (500) and the foldable backplate may be within a range of 0.1 mm to20 mm. As the difference between at least one width of the secondrelease film (500) and the foldable backplate satisfies the above range,the sticking-out of the pressure-sensitive adhesive (a part of thepressure-sensitive adhesive comes off) can be prevented and thetunneling problem due to lifting of the second release film (500) can besolved.

For example, the second release film (500) may be a film that foursurfaces are each extended from the first release film (300). The secondrelease film is attached so that each edge is extended to the outside ofthe foldable backplate, where the extended length (L3) may be in therange of 0.1 mm to 10 mm. The extended length means the shortestdistance from the edge end of the foldable backplate to the edge end ofthe second release film.

Then, the foldable backplate film according to the manufacturing methodaccording to the present invention shows the following structuralfeatures during manufacturing processes.

In one example, in the half-cut state, the first release film (300), thebase film (100) and the pressure-sensitive adhesive layer (200) maycomprise penetration regions penetrated along the cutting line, and theprotective film (500) may have a groove (H2) formed along the cuttingline.

The foldable backplate film that has undergone the cutting process has astructure in which a second release film (500), a pressure-sensitiveadhesive layer (200), a base film (100) and a protective film (400) aresequentially laminated, wherein the second release film (500) may not beformed with any penetration region and groove, and thepressure-sensitive adhesive layer (200) and the base film (100) maycomprise penetration regions along a cutting line and the protectivefilm (400) may comprise a groove (H2) along the cutting line. That is,the foldable backplate film comprises a protective film (400) having agroove (H2), a base film (100) laminated to surround the groove (H2) andhaving a first penetration region in communication with the groove (H2),a pressure-sensitive adhesive layer (200) laminated on the base film andhaving a second penetration region in communication with the firstpenetration region, and a second release film (500) laminated on thepressure-sensitive adhesive layer (200). The second release film (500)has no penetration region in communication with the second penetrationregion.

In addition, as described below, the present application can provide afoldable backplate film having excellent reliability and stabilitythrough material selection and physical property control of eachcomponent.

The storage elastic modulus of the base film at 20° C. may be 1 GPa to 5GPa, and for example, may be 1.5 GPa to 4 GPa or 2 GPa to 4 GPa. Thebase film according to the present application satisfies the range ofthe storage elastic modulus, whereby upon being applied to a backplateof a foldable display later, reliability is maintained even afterrepeated folding several times, the stress value generated upon foldingis minimized and it has a feature that can satisfy hardness sufficientto be capable of supporting the display panel.

In one example of the present application, a foldable backplate, inwhich the base film has an elongation at break of 20% or more and 200%or less at 20° C., is provided.

In another example, the elongation at break of the base film at 20° C.may be 20% or more and 200% or less, preferably 40% or more and 180% orless, more preferably 70% or more and 150% or less.

When the initial length of the base film is L1 and the length thatfracture occurs by stretching is L2, the elongation at break of thepolyimide base material means (L2−L1)/L1*100 (%).

The storage elastic modulus and the elongation at break were measured bythe method of KS M ISO527 using Zwick's UTM. By cutting the film to bemeasured to a width of 5 mm and a length of 60 mm or more and thensetting the gap between the grips to 40 mm, they can be each measured toa value measured while pulling the sample film at a speed of 20 mm/min.

In one example of the present application, a foldable backplate film, inwhich the base film has a thermal contraction rate of 0.1% or less at200° C., is provided.

In another example, the thermal contraction rate of the base film at200° C. may be 0.03% or more.

The thermal contraction rate means the degree of contraction in thedirection having the maximum contraction force when heat is applied tothe base film, and when the initial length of the base film is M1 andthe length shrunk in the contraction direction after heating at 200° C.for 2 hours is M2, it means the value of (M1−M2)/M1*100.

As the base film has a thermal contraction force in the above range, ithas a feature that deformation does not occur, because the contractionforce is low even when heat is applied in the backplate coating process.

In one example, the base film may be a polyimide base film. For example,the base film may be a polyimide base film satisfying at least one ormore of the storage elastic modulus, elongation at break and thermalcontraction rate as described above.

In the case of the foldable backplate film according to the presentapplication, the polyimide base film satisfying the above conditions isused, whereby it has excellent durability because plastic deformationdoes not occur in the backplate even when the folding and unfoldingoperations of the foldable display are repeated and it has a featurethat the strain generated upon folding can be restored without permanentdeformation upon defolding.

In addition, the thickness of the base film may be 20 μm or more and 120μm or less, and for example, it may be 30 μm or more and 100 μm or less,or 40 μm or more and 80 μm or less. As the base film has the abovethickness range, it has an excellent role as a support when used as abackplate of a foldable display later, a handling problem does not occurupon roll coating, and it has a feature that the stress value can beminimized because of a suitable curvature radius deviation.

The peel force of the first release film from the pressure-sensitiveadhesive layer may be 12 gf/inch or less at 23° C., and for example, itmay be 11 gf/inch or less, or 10 gf/inch or less. The peel force of thefirst release film from the pressure-sensitive adhesive layer has beenmeasured at an angle of 180° and a peel rate of 2400 mm/min using atexture analyzer (Stable Micro Systems), which is values obtained bymeasuring the foldable backplate film manufactured by the presentinvention at 23° C., respectively.

The first release film and the second release film may be siliconeseries.

The first and second release films are layers for protecting the verythin first and second pressure-sensitive adhesive layers, which refer totransparent layers attached to one side of the first and second adhesivelayers, where a film having excellent mechanical strength, thermalstability, moisture barrier properties, isotropy, and the like may beused. For example, acetate-based, polyester-based,polyethersulfone-based, polycarbonate-based, polyamide-based,polyimide-based, polyolefin-based, cycloolefin-based,polyurethane-based, silicone-based and acrylic resin films, such astriacetyl cellulose (TAC), and the like may be used, but it is notlimited thereto as long as it is a commercially available silicone-basedrelease film.

In one example of the present application, the first release film andthe second release film may further comprise an antistatic treatment toprevent damage to the display panel due to static electricity when theyare attached to the lower part of the display panel.

In one example of the present application, as the pressure-sensitiveadhesive layer, one or more selected from the group consisting of anacrylic pressure-sensitive adhesive layer, a rubber-basedpressure-sensitive adhesive layer and a silicone-basedpressure-sensitive adhesive layer may be used.

In another example, as the pressure-sensitive adhesive layer, an acrylicpressure-sensitive adhesive layer may be used.

In one example, the surface resistance of the first release film and thesecond release film may be 10¹⁰ Ω/sq or less under a condition of 500Vor less, and may be 3×10⁹ Ω/sq or less, or 1×10⁹ Ω/sq or less. Thesurface resistance of the first release film and the second release filmcan be measured using a concentric electrode on the PET back side of atest piece, and may be measured by the applied voltage of 500V, theapplied time of 10 sec, 25° C. and 55 RH % in MCT-HT800 (MitsubishiCorporation).

The first release film and the second release film have a surfaceresistance value in the above range due to the antistatic treatment, andhave a feature that damage to the display panel due to staticelectricity can be prevented when the first release film is peeled offlater and then attached to the lower part of the display panel.

In one example of the present application, the first release film andthe second release film may further comprise an antistatic treatment toprevent damage to the display panel due to static electricity when theyare attached to the lower part of the display panel.

The protective film may be attached by a process such as lamination,where the type of the protective film is not particularly limited, and aconventional product may be used. For example, as the protective film,products such as EPDC and LCFP composed of PET/PSA may be used.

In one embodiment, the protective film may have a groove formed alongthe cutting line. There is a difference in that as the manufacturingmethod according to the present application performs half-cutting in adirection from the first release film to the protective film, the grooveis formed in the protective film, whereas because the existing cuttingprocess performs half-cutting in a direction from the backplate to therelease film, the groove is formed in the release film.

Hereinafter, examples of the present invention will be described indetail so that those having ordinary knowledge in the technical field tothe present invention pertains can easily practice them. However, thepresent invention may be embodied in several different forms and is notlimited to the examples described herein.

EXAMPLE

According to the manufacturing method shown in FIG. 5 , a foldablebackplate film was manufactured. At this time, the difference (L1−L2)between the width of the second release film and the width of thefoldable backplate was in the range of 1.5 mm to 3 mm.

Comparative Example 1

A foldable backplate film was manufactured according to themanufacturing method shown in FIG. 3 .

Comparative Example 2

A foldable backplate film was manufactured in the same manner as inExample, except that the difference (L1−L2) between the width of thesecond release film and the width of the foldable backplate was lessthan 0.1 mm.

Comparative Example 3

A foldable backplate film was manufactured in the same manner as inExample, except that the difference (L1−L2) between the width of thesecond release film and the width of the foldable backplate was greaterthan 10 mm.

Experimental Example

After the foldable backplate films manufactured in Example andComparative Examples above were left at room temperature for 30 minutes,the presence or absence of sticking-out was visually observed, and as aresult, no defective product was observed in Example, whereas thesticking-out occurred in Comparative Example 1.

Also, in the foldable backplate film of Comparative Example 2, thesticking-out of the pressure-sensitive adhesive occurred, and in thefoldable backplate film of Comparative Example 3, tunneling occurred dueto the lifting of the second release film.

INDUSTRIAL APPLICABILITY

In the method for manufacturing a foldable backplate film according toan embodiment of the present application, the foldable backplate film ismanufactured by a method of cutting it in a direction from the releasefilm to the protective film upon half-cutting, and then release-changingthe release film to an extended release film, whereby it is possible toprevent the problem that the release film is not peeled off due to thesticking-out of the pressure-sensitive adhesive upon product handlingand transportation, or that the backplate comes with the release filmupon peeling of the release film.

1. A method for manufacturing a foldable backplate film comprising stepsof: preparing a foldable backplate comprising a base film and apressure-sensitive adhesive layer provided on one side of the base film;attaching a first release film to the opposite side of the side of thepressure-sensitive adhesive layer that is in contact with the base film;attaching a protective film to the opposite side of the side of the basefilm that is in contact with the pressure-sensitive adhesive layer;half-cutting the foldable backplate in a direction from the firstrelease film to the protective film along a cutting line dividing a bodypart and a pad part; peeling the first release film from thepressure-sensitive adhesive layer after the half-cutting step; andattaching a non-cut second release film to the position where the firstrelease film has been peeled off to manufacture the foldable backplatefilm, wherein at least one width of the second release film is greaterthan the width of the foldable backplate.
 2. The method formanufacturing a foldable backplate film according to claim 1, wherein adifference between the at least one width of the second release film andthe width of the foldable backplate is in a range of 0.1 mm to 20 mm. 3.The method for manufacturing a foldable backplate film according toclaim 1, wherein an edge of the non-cut second release film is extendedto the outside of the foldable backplate, and the extended length is ina range of 0.1 mm to 10 mm.
 4. The method for manufacturing a foldablebackplate film according to claim 1, wherein in the half-cut foldablebackplate, each of the first release film, the base film and thepressure-sensitive adhesive layer comprises a penetration regionspenetrated along the cutting line, and the protective film has a grooveformed along the cutting line.
 5. The method for manufacturing afoldable backplate film according to claim 1, wherein the foldablebackplate film has a structure in which the second release film, thepressure-sensitive adhesive layer, the base film and the protective filmare sequentially laminated, each of the pressure-sensitive adhesivelayer and the base film comprises a penetration regions along thecutting line, the protective film comprises a groove along the cuttingline, and the second release film does not comprise a penetration regionor a groove formed along the cutting line.
 6. The method formanufacturing a foldable backplate film according to claim 1, whereinthe base film has an elongation at break of 20% or more and 200% or lessat 20° C.
 7. The method for manufacturing a foldable backplate filmaccording to claim 1, wherein the base film has a thermal contractionrate of 0.1% or less at 200° C.
 8. The method for manufacturing afoldable backplate film according to claim 1, wherein the base film is apolyimide base film.
 9. The method for manufacturing a foldablebackplate film according to claim 1, wherein the base film has athickness of 20 μm or more and 120 μm or less.
 10. The method formanufacturing a foldable backplate film according to claim 1, whereinthe peel force of the first release film from the pressure-sensitiveadhesive layer is 12 gf/inch or less at 23° C.
 11. The method formanufacturing a foldable backplate film according to claim 1, whereinthe first release film and the second release film are silicone series.12. The method for manufacturing a foldable backplate film according toclaim 1, wherein the first release film and the second release film havea surface resistance of 10¹⁰ Ω/sq or less under a condition of 500V orless.
 13. The method for manufacturing a foldable backplate filmaccording to claim 1, wherein the protective film has a groove formedalong the cutting line.
 14. The method for manufacturing a foldablebackplate film according to claim 5, wherein the penetration region ofthe base film is a first penetration region that is in communicationwith groove in the protective film and the penetration region of thepressure-sensitive adhesive layer is a second penetration region that isin communication with the first penetration region.
 15. The method formanufacturing a foldable backplate film according to claim 1, whereinthe base film has a storage elastic modulus of 1 GPa to 5 GPa at 20° C.